1. Field of the Invention
This invention relates to an improvement in a high toughness and wear-resistance steel, and more particularly to an improvement in a high toughness and wear-resistance steel used as an excavating tool edge material for construction machines.
2. Description of the Prior Art:
Hitherto, it is well known that a tool edge material should be used in construction machines, such as, for example, bulldozers, power shovels, etc., as excavating soil, sand and rock requires high toughness and hardness. For example, when a hard rock having more than 3000 m./sec. of elastic wave velocity is excavated, the wear-resistance steel having more than 5 Kg./cm..sup.2 of toughness by Charpy impact value and more than 50 H.sub.R C of hardness is required. However, when excavating such hard rock with an excavating tool edge of such wear-resistance steel, there has been an inconvenience such that the excavating tool edge is heated by the friction with the rock to about 500.degree.C, and the steel is subjected to a tempering, thereby extremely decreasing the hardness thereof. In order to remove the above described inconvenience, the employment of an alloy steel consisting of C, Si, Mn, Cr, Mo, B and Fe has been considered. However, the alloy steel consisting of such components has had a disadvantage that the wear-resistance property thereof is significantly decreased when a hard rock as having more than 3000 m./sec. of elastic wave velocity is cut or excavated by the alloy steel.